New methodology may bring down percent of COVID positives

Total tests to be calculated instead of people tested
October 9, 2020

Seven months after Delaware began compiling its COVID-19 statistics, state officials have decided to use a different method to calculate the percentage of positive cases. That statistic landed Delaware on travel ban lists for New York and New Jersey several times over the summer, and the bans remained as of Oct. 6.

Dr. Karyl Rattay, director of the Division of Public Health, said Delaware will begin calculating its percent of positive COVID-19 cases using the total number of tests administered, instead of the number of people tested, as the state has been doing. The Centers for Disease Control, Johns Hopkins University, and states such as New York and New Jersey all calculate their percent of positive cases using total tests, Rattay said.

“The total test is the recommended approach by Johns Hopkins and the CDC, so it's important to us to present data consistent with those recommendations, and an important reason is so we can compare our data with other states,” she said during an Oct. 6 press conference.

Right now, Delaware's percent positive looks higher than other states because officials are using a different methodology, but once the new system begins, the percentages will drop, she said.

“It allows for more equal comparison across the states,” Rattay said. “You will see once we switch over to test-based positives that our percent positive will go down significantly. A big reason is your denominator or the bottom part of the calculation is total tests, which is much bigger than the total number of persons tested.”

She said the number will be posted on the My Healthy Community website this week.

Across the state, she said, the number of COVID-19 cases has ticked up, but there is no area that she would consider a hot spot. Areas of concern include the college town of Newark, and western Sussex County, where some long-term care facilities have posted recent positive cases.

“It's been concentrated in the young adult demographic,” said Gov. John Carney. “A good portion of that more recently from colleges and universities as students get back to campus, and off-campus parties and social events.”


Subscribe to the Daily Newsletter